BELGRADE, Yugoslavia — A United Nations plan for restoring peace in the Balkans has been halted at the armed barricades around Krajina, the Serbian-controlled stretch of disputed territory where rebels would rather wage war than remain part of Croatia.

The U.N. plan to send as many as 10,000 peacekeeping troops to Croatian trouble spots has won at least professions of support from all parties to the Yugoslav conflict, except for one bespectacled dentist who controls the angry enclave of Krajina.

Krajina is a smattering of towns and villages inhabited by nearly 200,000 Serbs. Its leader, Milan Babic, until recently played no role in the high-level diplomacy aimed at resolving the Yugoslav crisis.

But the meek-looking militant holds sway over one of the most independent of the renegade factions of the fractured Yugoslav federal army, and he has threatened to kill any foreign troops who enter his territory uninvited.

Babic's rejection of U.N. intervention has undermined what many here see as the last best chance of stopping a war that has already claimed 10,000 lives.

U.N. Undersecretary General Marrack Goulding, who has been shuttling among Serbian and Croatian warlords this week, said Tuesday after visiting Krajina and other parts of Croatia that the parties to the conflict are effectively deadlocked.

Goulding described Babic's position as "irreconcilable" with certain conditions of the U.N. deployment plan. He said there is also some resistance on the side of the Croatian leadership.

"There are one or two points . . . on which both sides have reservations," he told reporters after talks with Croatian President Franjo Tudjman in Zagreb. He did not specify the obstacles.

Babic made his objections clear in a statement to Belgrade Radio, complaining that the U.N. deployment plan would effectively define his territory as part of Croatia, which has seceded from Yugoslavia and been recognized as an independent nation by at least 30 countries.

"The basic objection is that it treats Krajina as a part of Croatia," Babic said after meeting with Goulding late Monday in the Krajina stronghold of Knin. "This is naturally unacceptable from our side, and that is the basic cause of the armed conflict."

The U.N. plan brokered by special envoy Cyrus R. Vance, a former U.S. secretary of state, requires all units of the federal army to leave Croatia and all armed guerrillas inside three specified crisis zones--one of which is Krajina--to demobilize and turn in their weapons.

It does not specifically define Krajina as part of Croatia, but Croatian sovereignty over the region is implied by the plan's requirement that the army depart.

Babic said he proposed that peacekeepers be stationed along Krajina's "border" with Croatia, although the Serbian-controlled region is neither contiguous nor ethnically homogenous. Such a deployment would also serve to cement the Serbian grip on the area, making it unlikely that Zagreb officials would agree to modify the U.N. plan in this way.

"By disarming and intervening in Krajina alone, they will upset the existing de facto state to our disadvantage," Babic said. "We expect the U.N. to be more flexible."

The U.N. plan that was accepted as part of a Jan. 3 cease-fire agreement calls for "full compliance" by all parties with the terms hammered out by Vance. It also rejects any changes in Yugoslavia's internal borders by force and insists that the combatants tackle territorial issues at the negotiating table.

Vance's text describes the U.N. peacekeeping deployment as a temporary measure to prevent fighting long enough for the sides to work out a peaceful settlement.

But Serbs in the Krajina fear that turning over their security to the United Nations would sacrifice their greatest advantage, which is possession and control of the territory they want separated from independent Croatia.

"Babic considers the U.N. plan to be the basis for a political agreement, although it's not," said a Western diplomat in Belgrade. "He is objecting to every condition that implies the Krajina is part of Croatia."

Krajina, which means "military frontier," has a long tradition as a warrior haven. The region was settled by Serbs four centuries ago when the Austro-Hungarian Empire, which then ruled Croatia, gave land and refuge to those fleeing Ottoman-ruled Serbia in return for guarding the European empire from Turkish attack.

About one-third of Croatia is now occupied by Serbs who gained exclusive control of the area with the backing of the Yugoslav federal army.

The former federal defense minister, Gen. Veljko Kadijevic, earlier this month endorsed the Vance plan, along with Tudjman and Serbian President Slobodan Milosevic. But Kadijevic resigned four days later after army renegades shot down a European Community helicopter, killing all five truce monitors on board. The new defense minister, Gen. Blagoje Adzic, is a known hard-liner fiercely opposed to Croatian rule over Serbian communities.